Color-proofing is the procedure used by the printing industry for creating representative images that replicate the appearance of printed images without the cost and time required to actually set up a high-speed, high-volume printing press to print an example of the images intended. One such color proofer is a lathe bed scanner which utilizes a thermal printer having half-tone capabilities. This printer is arranged to form an image on a thermal print medium, or writing element, in which a donor transfers a dye to the writing element upon a sufficient amount of thermal energy. This printer includes a plurality of diode lasers which can be individually modulated to supply energy to selected areas of the medium in accordance with an information signal.
A print-head includes one end of a fiber optic array having a plurality of optical fibers that are coupled to the diode lasers for transmitting the signals from the laser to the print head. The writing element is supported on a rotatable imaging drum, and the print-head with the fiber optic array is movable relative to the longitudinal axis of the drum. The dye is transferred to the writing element as the radiation, transferred from the diode lasers to the donor element by the optical fibers, is converted to thermal energy in the donor element.
The cylindrical-shaped imaging drum includes a lip portion at both ends having a depth substantially equal to the depth of the writing element for supporting the writing element therein. The donor, which is slightly wider in width than the writing element, rests its center portion atop the writing element with its edges resting on the lip portions. This configuration eliminates any crease from occurring at the edges of the donor as they are drawn over the writing element during the loading of the donor. Such creases create undesirable effects on the writing element during printing.
Although the presently known and utilized scanner is satisfactory, it is not without drawbacks. The lip portions are permanently affixed to the imaging drum at its ends, and when a narrow-width writing element is placed on the drum, a gap is created between each lip portion and the edge of the writing element to which it is adjacent. The donor is placed atop the writing element with its center portion atop the writing element, and it extends outwardly over the gap so that its edges rest atop the lip portion. Consequently, the donor will not have adequate support at its portion directly above the gap. This will obviously result in undesirable creases in the donor sheet. Alternatively, a new imaging drum with a smaller width between the lip portions may be installed. This is also undesirable due to the cost of a new drum, downtime and the labor required to install it.
Consequently, a need exists for improvements in the construction of the lathe bed scanner so as to overcome the above-described shortcomings.